ecore_wl2: Make www events opt-in

Now we must set EFL_WAYLAND_ENABLE_WWW to turn on www.  (Note:
this does NOT re-enable any visual effect, it merely controls
the event infrastructure that can be used to let a client
know when its window is mapped or moving)

This wasn't really disabled properly earlier, so disable it now
for a slight performance win when dragging windows (and a major
reduction in log chatter when debugging wayland)

src/lib/ecore_wl2/ecore_wl2_display.c

@@ -187,7 +187,7 @@ _cb_global_add(void *data, struct wl_registry *registry, unsigned int id, const
                                    &_zxdg_shell_listener, NULL);
      }
    else if ((eina_streq(interface, "www")) &&
-            (!getenv("EFL_WAYLAND_DISABLE_WWW")))
+            (getenv("EFL_WAYLAND_ENABLE_WWW")))
      {
         Ecore_Wl2_Window *window;